A technique is known in which an optical fiber cable is configured with optical fiber assemblies each formed by tying a plurality of optical fibers in a bundle as an optical fiber unit. In such a case, a common method is to wind a coarse string (bundling member) around the bundle of the optical fibers, thereby identifying the optical fiber unit with the color of the bundling member while restraining the bundle of the optical fibers from spreading out.
With regard to such a bundling member, Patent Literature 1 discloses a method of providing water resistance to an optical fiber unit by using water absorptive yarn as a bundling member. Further, Patent Literature 2 discloses a method of facilitating identification of an optical fiber unit by coloring a bundling member thereof with a single color.